Image reader and image formation system

Abstract

To acquire a result for new shading compensation.SOLUTION: An image reader comprises: a surface white reference member; a surface reading unit 104 for reading a script or the surface white reference member; an optical system motor 225 for moving the surface reading unit 104 into a first region for reading the script and a second region for reading the surface white reference member in a direction of transferring the script; and a CPU 301 for performing shading compensation. The CPU 301 performs first reading operation of moving the surface reading unit 104 from the outside of the second region to the inside of the second region and making the surface white reference member be read in the second region; after the first reading operation, performs second reading operation of again moving the surface reading unit 104 from the outside of the second region to the inside of the second region and making the surface white reference member be read in the second region; and performs shading compensation using a first reading result of the first reading operation and a second reading result of the second reading operation.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image reading device that reads an image from a document. [Background technology]

[0002] An image reading device can read a document by "fixed reading," which reads a document placed on a document glass, or by "floating reading," which reads a document transported by an automatic document feeder (hereinafter referred to as "ADF"). Floating reading allows multiple documents to be read continuously. An image reading device has a reading unit for reading documents. In fixed reading, the reading unit moves in one direction below the document glass, reading the document line by line, with a direction perpendicular to the direction of movement being considered as one line. In flow reading, the reading unit is fixed in position, and reads the document passing the reading position by the ADF line by line, with a direction perpendicular to the document transport direction being considered as one line. The direction of one line is the main scanning direction, and the direction in which the reading unit moves, or the document transport direction, is the sub-scanning direction.

[0003] An image reading device is connected to an image forming device to form a copier. Copiers are required to shorten the first copy output time, which is the time it takes from starting to read a single page of an original to outputting the resulting copy.

[0004] Image reading devices perform shading processing as a preparation for reading a document. Shading processing is a process that generates shading correction data to align the reading results (read data) of a white reference member with the reference data. The shading correction data is a correction value for reading each pixel in the main scanning direction of the document at a uniform density, regardless of uneven sensitivity of the reading sensor or uneven light intensity of the light source. Shading correction is performed using the shading correction data, making it possible to read an image accurately. Shading correction is performed, for example, by adjusting the light emission intensity of the reading unit's light source or the sensitivity of the light receiving element, or by correcting the read image.

[0005] In shading processing, accurate shading correction data cannot be obtained if foreign matter such as dust adheres to the white reference member. For example, if foreign matter adheres to the white reference member, the read data, which should be a constant value, becomes an abnormal value at the position of the foreign matter. The shading correction data generated based on such read data will have an abnormal value only at the position of the foreign matter. When shading correction is performed using such shading correction data, a white streak will appear in the read image of the original document at the position of the foreign matter, for example. In response to this, Patent Document 1 identifies the position of the foreign matter based on the results of multiple scans of the white reference member at different positions in the sub-scanning direction, and corrects the data for the foreign matter position in the shading correction data. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-313793 Summary of the Invention [Problem to be solved by the invention]

[0007] In the past, shading correction was performed based on the results obtained in a single movement of the reading unit, but there was room for further improvement in obtaining results for shading correction. In view of the above-mentioned problems, the main object of the present invention is to obtain new results for shading correction. [Means for solving the problem]

[0008] The image reading device of the present invention comprises a reference member, a reading means for reading a document or the reference member, a moving means for moving the reading means in the document transport direction to a first area for reading the document and a second area for reading the reference member, and a control means for performing shading correction, wherein the control means moves the reading means in the transport direction from outside the second area to inside the second area and performs a first reading operation to read the reference member in the second area, and after performing the first reading operation, moves the reading means again from outside the second area to inside the second area and performs a second reading operation to read the reference member in the second area, and performs the shading correction using the first reading result read in the first reading operation and the second reading result read in the second reading operation. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain new results for shading correction. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an external perspective view of an automatic document reading device. [Figure 2] FIG. [Figure 3] FIG. 2 is a diagram illustrating the internal configuration of the automatic document reading device. [Figure 4] Control system configuration diagram. [Figure 5] 10(a) to 10(e) are explanatory diagrams of shading processing. [Figure 6] (a) and (b) are explanatory diagrams of shading processing. [Figure 7] 10A to 10C are diagrams illustrating the influence of foreign matter adhering to the white reference member. [Figure 8] 10 is a flowchart showing an abnormal pixel detection process. [Figure 9] 10(a) to 10(c) are explanatory diagrams of abnormal pixel detection. [Figure 10] 10 is a flowchart showing a correction process for an abnormal pixel. [Figure 11]FIG. 10 is a diagram illustrating the results of abnormal pixel correction. [Figure 12] 10 is a flowchart showing a document reading process. [Figure 13] 10 is a flowchart showing an abnormal pixel detection process. [Figure 14] FIG. [Figure 15] 10 is a flowchart showing an abnormal pixel correction process. [Figure 16] 10 is a flowchart showing a document reading process. [Figure 17] FIG. 4 is an explanatory diagram of a sensor provided below the platen glass. [Figure 18] 10 is a flowchart showing a document reading process. [Figure 19] 10 is a flowchart showing a document reading process. [Figure 20] 10 is a flowchart showing a document reading process. [Figure 21] FIG. 1 is a diagram illustrating the configuration of an image forming system. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] (First embodiment) 1 is a perspective view of the appearance of an automatic document reading device including an image reading device according to this embodiment. The automatic document reading device 10 includes an image reading device (hereinafter referred to as a "reader 40") that reads a document, and an ADF 20 that automatically transports the document to a reading position of the document by the reader 40. The ADF 20 functions as a sheet transport device that transports sheet-like documents to the reader 40.

[0013] The automatic document reader 10 has an operation unit. FIG. 2 is an explanatory diagram of the operation unit. The operation unit 90 is a user interface having an input interface and an output interface. In FIG. 2, the input interface is a group of operation keys 92 including a start key 93. The input interface may also include, for example, a touch panel. In FIG. 2, the output interface is a display unit 91. The output interface may also include, for example, a speaker.

[0014] FIG. 3 is a diagram showing the internal configuration of the automatic document reading device 10. The reader 40 is provided with a glass document table 101 between it and the ADF 20. The ADF 20 is rotatably supported by the reader 40 via a hinge (not shown) so that it can be opened and closed relative to the glass document table 101. The reader 40 and the ADF 20 each have a reading unit for reading a document. The reader 40 has a front side reading unit 104 that reads a first side of the document (hereinafter, the first side may also be referred to as the "front side"). The ADF 20 has a back side reading unit 212 that reads a second side of the document (hereinafter, the second side may also be referred to as the "back side") that is different from the first side. The document may be blank, or may have an image formed on one or both sides.

[0015] The ADF 20 includes a document tray 121 on which documents are loaded and a discharge tray 122 onto which the scanned documents are discharged. The document tray 121, together with a lower transport guide 123 of the ADF 20, constitutes a sheet loading section 120. The document tray 121 includes, on its document loading surface, width restriction plates 125 that are movable in a width direction perpendicular to the document transport direction. The width restriction plates 125 restrict the position of the documents placed on the document tray 121 in the width direction. Two width restriction plates 125 are provided in the width direction, and the documents placed on the document tray 121 are sandwiched between the two width restriction plates 125.

[0016] The two width restriction plates 125 move in conjunction with each other by moving one of them via an interlocking mechanism (not shown), such as a rack-and-pinion mechanism, arranged inside the document tray 121. In this embodiment, the center of document transport is at the center in the width direction, and the two width restriction plates 125 are configured to move closer to or farther away from the center in the width direction. This ensures that the center of document transport is at the same position regardless of the size of the document. Furthermore, by measuring the distance between the two width restriction plates 125, the width size of the document placed on the document tray 121 can be detected.

[0017] The ADF 20 includes a pickup roller 111 as a conveying rotating body, and a separation drive roller 112 and a retard roller 113 that form a separation roller pair to feed paper from the document tray 121. The ADF 20 also includes a registration roller pair 114a, 114b, a lead roller pair 115a, 115b, a conveying roller pair 117a, 117b, and a discharge roller pair 119a, 119b to convey the fed document.

[0018] A first document presence / absence detection sensor 204 and a second document presence / absence detection sensor 205 are provided between the pickup roller 111 and the separation roller pair. A post-separation sensor 207 is provided on the transport path between the separation roller pair and the registration roller pair 114a, 114b. A read sensor 210 is provided on the transport path between the registration roller pair 114a, 114b and the lead roller pair 115a, 115b. A back-side reading unit 212 is provided on the transport path between the lead roller pair 115a, 115b and the transport roller pair 117a, 117b.

[0019] The reader 40 has a front surface reading glass 102 on the same surface as the document glass 101, and has a front surface reading unit 104 inside. The front surface reading glass 102 is provided with a front surface white reference member 103 facing inward of the reader 40, and a back surface white reference member 110 facing outward of the reader 40. The front surface white reference member 103 and the back surface white reference member 110 are used for shading processing. At least the front surface white reference member 103 is an inexpensive product that uses a sheet with an uneven surface.

[0020] As will be described in detail later, shading correction is performed based on the results of reading the front white reference member 103 by the front reading unit 104. However, because the front white reference member 103 has an uneven surface, it may not be possible to obtain accurate shading correction data. Fluctuations in shading correction data due to unevenness result in fluctuations in the brightness of the read image when the original is read. Fluctuations in brightness due to unevenness on the sheet surface are smaller than fluctuations in brightness due to foreign matter. For this reason, it is difficult to detect and correct unevenness on the sheet surface in the same way as foreign matter.

[0021] It is possible to obtain shading correction data that suppresses the effects of foreign matter and unevenness based on multiple read data obtained by multiple readings of the front white reference member 103. However, because foreign matter causes large fluctuations in brightness, it is necessary to make the read area (shading area) of the front white reference member 103 large in order to suppress the effects of foreign matter.

[0022] The front surface reading unit 104 is disposed on a guide 109 and is movable along the guide 109. The front surface reading unit 104 is located directly below the front surface reading glass 102 when reading a document transported by the ADF 20, and moves along the guide 109 when reading a document placed on the document glass 101. In this embodiment, the operation mode for reading a document transported by the ADF 20 is called a "skimming mode," and the operation mode for reading a document placed on the document glass 101 is called a "fixed reading mode." The skimming mode is set when the first document presence / absence detection sensor 204 detects a document loaded on the document tray 121 or when the user explicitly instructs it via the operation unit 90 or the like. The fixed reading mode is set when a document placed on the document glass 101 is detected or when the user explicitly instructs it via the operation unit 90.

[0023] The document transport operation by ADF 20 will now be described. Pickup roller 111 is disposed so as to be swingable by arm 111a. Arm 111a is driven to move up and down, causing pickup roller 111 to contact and separate from the uppermost document in a stack of documents stacked on document tray 121. A locking mechanism that locks regulating plate 130 that contacts the edge of the document is provided in conjunction with arm 111a. This locking mechanism locks regulating plate 130 in a position that regulates the leading edge of the document when pickup roller 111 is raised. Furthermore, when pickup roller 111 is lowered, the locking mechanism unlocks regulating plate 130, allowing the document to pass through.

[0024] Detecting member 160 of first document presence detection sensor 204 and detecting member 150 of second document presence detection sensor 205 are arranged side by side in the width direction upstream of regulating plate 130 in the document transport direction. Detecting member 160 and detecting member 150 are arranged downstream of pickup roller 111 in the document transport direction, specifically downstream of the position where pickup roller 111 descends and contacts the document. First document presence detection sensor 204 outputs an ON signal when detecting member 160 is pressed downward by the document and rotated. Second document presence detection sensor 205 outputs an ON signal when detecting member 150 is pressed upward by the document and rotated. The presence or absence of a document on document tray 121 is determined based on the signals output from first document presence detection sensor 204 and second document presence detection sensor 205.

[0025] The document fed by the pickup roller 111 is separated into individual sheets by the separation drive roller 112 and the retard roller 113 and conveyed. A torque limiter is disposed in the rotation support structure of the retard roller 113, and the retard roller 113 follows the separation drive roller 112 when one document sheet is fed, and does not rotate when two or more documents are fed. In this way, the document sheets are separated one by one. Note that the retard roller 113 may be driven in the opposite direction to the conveying direction. In the fixed reading mode, the front surface reading unit 104 moves directly below the conveying guide plate 211 to read the document being conveyed simultaneously with the lowering of the pickup roller 111.

[0026] The leading and trailing edges of the document that has passed through the pair of separation rollers are detected by a post-separation sensor 207. The detection result of the post-separation sensor 207 serves as a reference for the timing of raising and lowering the pickup roller 111 and the timing of starting and stopping the pickup roller 111. The pickup roller 111 and the separation drive roller 112 are driven by the same drive source.

[0027] The pair of registration rollers 114a and 114b correct skew of the original. After skew correction by the pair of registration rollers 114a and 114b, the original is transported toward the front surface reading glass 102 by the pair of lead rollers 115a and 115b. The drive timing of the pair of registration rollers 114a and 114b and the pair of lead rollers 115a and 115b is controlled by the detection result of the post-separation sensor 207. A transport guide plate 211 is disposed opposite the front surface reading glass 102. The transport guide plate 211 guides the original passing between the pair of registration rollers 114a and 114b and the pair of lead rollers 115a and 115b so that the original does not lift off the front surface reading glass 102. The position of the transport guide plate 211 is the position at which the original is read by the front surface reading unit 104. The pair of registration rollers 114a and 114b and the pair of lead rollers 115a and 115b are driven by the same drive source.

[0028] When reading one side of a document, the image on the front side of the document is read by a front side reading unit 104 through a front side reading glass 102. The front side reading unit 104 includes an LED (Light Emitting Diode) 105 as a light source, a lens array 107, and a reading sensor 108 as a line sensor.

[0029] The front surface reading unit 104 illuminates the surface (read surface) of the document using an LED 105. Light reflected from the surface of the document passes through a lens array 107 and is received by a reading sensor 108. The reading sensor 108 has a plurality of light receiving elements arranged in a line, and each light receiving element receives the reflected light. Each light receiving element performs photoelectric conversion on the reflected light, and generates and outputs image data as the document reading result. The plurality of light receiving elements are arranged in a direction perpendicular to the document transport direction, and perform photoelectric conversion line by line. The LED 105 emits light linearly in the arrangement direction of the light receiving elements. With this configuration, the direction perpendicular to the document transport direction is the main scanning direction, and the document transport direction is the sub-scanning direction.

[0030] The document whose front side has been read by the front side reading unit 104 is discharged onto a discharge tray 122 by a pair of conveying rollers 117a and 117b and a pair of discharging rollers 119a and 119b. The pair of conveying rollers 117a and 117b and the pair of discharging rollers 119a and 119b are driven by the same driving source.

[0031] When reading both sides of a document, the image on the front side of the document is read by the front side reading unit 104, and the image on the back side of the document is read by the back side reading unit 212. The back side reading unit 212 has the same configuration as the front side reading unit 104, and includes an LED 214 which is a light source, a lens array 215, and a reading sensor 216 which is a line sensor. The back side reading unit 212 reads the back side of the document whose front side has been read by the front side reading unit 104. The document reading operation by the back side reading unit 212 is the same as that of the front side reading unit 104. The main scanning direction and the sub-scanning direction are also the same.

[0032] In the fixed reading mode, which does not use the ADF 20, an original is placed on the platen glass 101 with the reading surface facing the reader 40. In this case, the original on the platen glass 101 does not move, and the front surface reading unit 104 reads the original while moving directly below the platen glass 101 along the guide 109. The reading operation of the front surface reading unit 104 is the same as in the flow reading mode. In the fixed reading mode, the movement direction of the front surface reading unit 104 is the sub-scanning direction, and the direction perpendicular to the movement direction is the main scanning direction.

[0033] 4 is a configuration diagram of a control system that controls the operation of the automatic document reading device 10. The control system includes a configuration provided on the reader 40 side and a controller 310. The controller 310 may be provided within the automatic document reading device 10, but may also be provided on an external device, for example, on the image forming device side when the automatic document reading device 10 is connected to an image forming device. When the automatic document reading device 10 is connected to such an image forming device, it constitutes, for example, a copier, a facsimile machine, a multifunction peripheral, an MFP (Multi Function Peripheral), etc.

[0034] The reader 40 is provided with an information processing device including a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, and a RAM (Random Access Memory) 303. The reader 40 also includes an image memory 305, an image processing unit 306, a shading memory 307, and an image transfer unit 304 as a control system. The image transfer unit 304 is communicably connected to a controller 310 via an image transfer line 402. The reader 40 also includes an optical system HP sensor 226 and an optical system motor 225 in addition to the components described in FIG. 3. The ADF 20 also includes a feed clutch 223 and a transport motor 224 in addition to the components described in FIG. 3.

[0035] The CPU 301 controls the operations of the reader 40 and the ADF 20 by executing a computer program stored in the ROM 302. The RAM 303 provides a working area for the CPU 301 when it executes processing. The CPU 301 is communicably connected to each component of the reader 40 and the ADF 20 via a bus. The CPU 301 is communicably connected to the controller 310 via a communication line 401.

[0036] The CPU 301 controls the drive of a transport motor 224 for driving the rollers for transporting the document, in order to realize the document transport function of the ADF 20. The transport motor 224 is connected to the pickup roller 111 and the separation drive roller 112 via a feed clutch 223. By disconnecting the feed clutch 223, the transport of the document can be stopped at a position P (see FIG. 3) just before the document reaches the pair of registration rollers 114a and 114b. The conveying motor 224 is connected to and drives the registration roller pair 114a, 114b, the lead roller pair 115a, 115b, the conveying roller pair 117a, 117b, and the discharge roller pair 119a, 119b.

[0037] The transport motor 224 is a pulse motor. The CPU 301 controls the drive of the transport motor 224 by controlling the number of drive pulses. The number of drive pulses correlates with the transport distance of the document being transported. Therefore, the CPU 301 controls each load based on the transport distance calculated from the number of drive pulses, and transports the document.

[0038] The CPU 301 detects the presence or absence of a document in the document tray 121 based on the detection results of the first document presence / absence detection sensor 204 and the second document presence / absence detection sensor 205. The CPU 301 detects the position of the document being transported along the transport path based on the detection results of the post-separation sensor 207 and the lead sensor 210.

[0039] The optical system motor 225 is a drive source for moving the front surface reading unit 104 in the sub-scanning direction along the guide 109. The optical system motor 225 is driven and controlled by the CPU 301. The optical system HP sensor 226 is a sensor for detecting that the front surface reading unit 104 is located at the home position (HP).

[0040] The front side reading unit 104 has the LED 105 and the reading sensor 108 as described above. The front side reading unit 104 receives the reflected light of the light irradiated from the LED 105 onto the transported document by the reading sensor 108, and generates image data as the reading result. The back side reading unit 212 has the LED 214 and the reading sensor 216 as described above. The back side reading unit 212 receives the reflected light of the light irradiated from the LED 214 onto the transported document by the reading sensor 216, and generates image data as the reading result. The image data output from each of the front side reading unit 104 and the back side reading unit 212 is temporarily stored in the image memory 305. The image data represents the read image.

[0041] The document reading process by the front surface reading unit 104 and the back surface reading unit 212 is controlled by the CPU 301. When the lead sensor 210 detects a document, the CPU 301 causes the front surface reading unit 104 and the back surface reading unit 212 to perform the document reading process.

[0042] The image processing unit 306 performs predetermined image processing to correct the read data (read image) stored in the image memory 305. The shading memory 307 is connected to the image processing unit 306 and stores shading correction data, which will be described later. The CPU 301 can read and write data stored in the shading memory 307 via the image processing unit 306. The image transfer unit 304 transfers the image data that has been image-processed by the image processing unit 306 to the controller 310 via an image transfer line 402.

[0043] The controller 310 controls the overall operation of the image reading system, including the reader 40 and the ADF 20. The controller 310 includes a CPU 311, a ROM 312, a RAM 313, an image transfer unit 314, and an image memory 315. These are communicatively connected via a bus. The operation unit 90 is also connected to this bus.

[0044] The CPU 311 controls the operation of the controller 310 by executing a computer program stored in the ROM 312. The CPU 311 accepts instructions and the like input through the operation unit 90. The CPU 311 displays messages, scanned images, and the like on the display unit 91 of the operation unit 90. The RAM 313 provides a working area for the CPU 311 when it executes processing. The image transfer unit 314 acquires image data from the image transfer unit 304 of the reader 40 via the image transfer line 402 and stores the image data in the image memory 315.

[0045] The CPU 311 cooperates with the CPU 301 to control image reading by the automatic document reader 10. To this end, the CPU 311 transmits and receives control data such as instructions relating to image reading control to and from the CPU 301 via a communication line 401.

[0046] For example, CPU 311 acquires an instruction to start an image reading job from operation unit 90 and transmits the instruction to start reading to CPU 301. The instruction to start an image reading job includes information such as an instruction for black and white reading / color reading, reading resolution, a document size to be read, and an instruction to start an image reading job. The instruction to start reading includes control information such as an instruction to start document feeding and a document reading instruction. The instruction to start document feeding includes information on reading resolution, and the instruction to read a document includes information on the document size to be read. CPU 311 also acquires information indicating the status of automatic document reading device 10 from CPU 301 and causes operation unit 90 to display a message to the user according to the status of the device.

[0047] (Shading correction) The front white reference member 103 and the back white reference member 110 are white reference plates for creating white level correction data based on shading. The front white reference member 103 is used to generate shading correction data for the front reading unit 104. The back white reference member 110 is used to generate shading correction data for the back reading unit 212. The shading correction data for the front reading unit 104 is generated by image processing the reading result (read data) of the front white reference member 103 by the front reading unit 104. The shading correction data for the back reading unit 212 is generated by image processing the reading result (read data) of the back white reference member 110 by the back reading unit 212. The shading correction data is generated before the document is read.

[0048] 5 and 6 are explanatory diagrams of the shading process of the front surface reading unit 104. FIG. 5(a) shows a state in which the front surface reading unit 104 starts moving from position P1, which is the home position. In other words, the front surface reading unit 104 moves from outside the area for reading the front surface white reference member 103 to inside the area. FIG. 5(b) shows a state in which the front surface reading unit 104 has moved from position P1 to position P3 via position P2. FIG. 5(c) shows a state in which the front surface reading unit 104 has moved from position P3 to position P1 via position P2. FIG. 5(d) shows a state in which the front surface reading unit 104 has moved from position P1 to position P3 via position P2. FIG. 5(e) shows a state in which the front surface reading unit 104 has moved to the reading start position Ps. When performing fixed reading in fixed reading mode, the front surface reading unit 104 reads the document at the reading start position Ps. When performing skimming in the skimming mode, the front surface reading unit 104 reads the document while moving in the sub-scanning direction from the reading start position Ps. In other words, the front surface reading unit 104 moves from outside the area for reading the document to inside the area.

[0049] In the shading process of the front surface reading unit 104, the front surface reading unit 104 reads the front surface white reference member 103 while moving from position P1, which is directly below the front surface white reference member 103, to position P3. FIG. 6(a) is an example diagram of the reading result of one line. FIG. 6(a) shows the reading level (e.g., luminance value) of each position (each pixel) in the main scanning direction. In the shading process, a correction coefficient for each pixel is derived so that the reading level for each pixel as shown in FIG. 6(a) is corrected to a predetermined white level Tgtw as shown in FIG. 6(b). This correction coefficient is shading correction data for the front surface and is stored in the shading memory 307.

[0050] The back surface reading unit 212 is fixed to the ADF 20, and during shading processing, it reads the back surface white reference member 110 without moving like the front surface reading unit 104. Based on the reading result (reading level) of the back surface white reference member 110 by the back surface reading unit 212, a correction coefficient for each pixel is derived, just like for the front surface. This correction coefficient is shading correction data for the back surface, and is stored in the shading memory 307.

[0051] The shading correction data is composed of data (correction values) for the number of pixels in the main scanning direction for each of the three primary colors (red, green, and blue) of the light source. When reading an original, for example, each time one line of the original is read, the image processing unit 306 corrects the read image (read data) for one line using the shading correction data stored in the shading memory 307 to generate image data. The image processing unit 306 stores the image data generated by the correction in the image memory 305.

[0052] (Abnormal pixel detection) If foreign matter such as dust adheres to the front white reference member 103 or the back white reference member 110, the reading level of the reading result will contain abnormal values, making it impossible to obtain accurate shading correction data. Figure 7 is an explanatory diagram of the effect when foreign matter adheres to the white reference member.

[0053] Figure 7(a) shows the read level at each position (each pixel) in the main scanning direction, which is the result of reading a white reference member with foreign matter (dust) attached. Due to the influence of the dust, there are pixels where the read level is abnormally low compared to other pixels. Figure 7(b) shows the shading correction data obtained from the read result of Figure 7(a). The correction value of the pixel where the dust is attached is abnormally high compared to the correction values ​​of other pixels. Figure 7(c) shows a copied image obtained by performing shading correction using such shading correction data when copying an original. A white streak image appears at the location of the dust.

[0054] A position (pixel) in the main scanning direction where an abnormal reading result occurs due to foreign matter adhering to the white reference member in this way is called an abnormal pixel. This section explains how to detect an abnormal pixel when foreign matter has adhered to the front white reference member 103. In this embodiment, abnormal pixels on the front white reference member 103 are detected by detecting pixels with abnormal values ​​from the shading correction data (shading correction coefficients). The shading correction data of the detected abnormal pixel is corrected by interpolating with the shading correction data adjacent to the abnormal pixel.

[0055] FIG. 8 is a flowchart showing the abnormal pixel detection process. FIG. 9 is an explanatory diagram of abnormal pixel detection. As shown in FIG. 9(a), a case will be described where foreign matter (dust) is attached to the positions of pixels A and B in the main scanning direction. Pixel A is located at position P1 in the sub-scanning direction. Pixel B is located between positions P2 and P3 in the sub-scanning direction.

[0056] The CPU 301 of the reader 40 moves the front surface reading unit 104 to position P1 (home position) in FIG. 5 (S110). Hereinafter, position P1 may be referred to as the "HP position." If the front surface reading unit 104 is already at the HP position, the process of S110 is omitted. Whether the front surface reading unit 104 is at the HP position is determined based on the detection result of the optical system HP sensor 226.

[0057] The CPU 301 performs black level adjustment at the HP position by having the front surface reading unit 104 read the front surface white reference member 103 with the LED 105 turned off (S111). In black level adjustment, brightness unevenness in the main scanning direction is corrected with the LED turned off (dark), and output variations in the front surface reading unit 104 in the dark are mainly corrected. By correcting output variations in the dark, brightness unevenness in the main scanning direction when reading a black document is corrected, and at the same time, the input dynamic range can be secured.

[0058] The CPU 301 reads the front white reference member 103 using the front surface reading unit 104 with reading settings set so that the maximum value of the reading result (brightness value) is darker than during normal image reading. To do this, the CPU 301 turns on the LED 105 at the HP position (S112) and reads the front surface white reference member 103 using the front surface reading unit 104 (S113). The CPU 301 obtains reference shading correction data for detecting abnormal pixels based on the reading result (read data). The reference shading correction data is obtained from the arithmetic average of the read data values ​​for each pixel in the main scanning direction. Figure 9(b) is an example diagram of the reference shading correction data. At the position of pixel A, the read data value is darker (lower) than the surrounding pixels due to the influence of dust, so the correction coefficient for correcting it to white is higher than the surrounding pixels.

[0059] The CPU 301 moves the front surface reading unit 104 from the HP position to position P3 using the optical system motor 225 (S114). As a result, the front surface reading unit 104 moves from the state shown in FIG. 5(a) to the state shown in FIG. 5(b). The CPU 301 reads the front surface white reference member 103 while moving the front surface reading unit 104 based on the reference shading correction data (S115). Here, the front surface reading unit 104 reads the front surface white reference member 103 between positions P2 and P3 multiple times while moving from position P1 to position P3 in FIG. 5(b).

[0060] The CPU 301 waits until the front surface reading unit 104 moves to position P3 and finishes reading the front surface white reference member 103 (S116: N). When reading of the front surface white reference member 103 is finished (S116: Y), the CPU 301 performs abnormal pixel detection on the front surface white reference member 103 (S117). The CPU 301 detects abnormal pixels from the arithmetic average of the values ​​of the read data for each pixel in the main scanning direction.

[0061] FIG. 9(c) shows the average value of the read results (read data) obtained by the process of S115. Here, a luminance value is obtained as the read result. Due to shading correction using the reference shading correction data, each pixel in the main scanning direction has a uniform luminance overall. However, at the position of pixel A, the luminance value is high because the front white reference member 103 is read in a state where the shading correction coefficient is high due to the influence of dust. At the position of pixel B, the luminance value is low because dust is read.

[0062] The CPU 301 compares the scanned data with a predetermined dust detection threshold and detects pixels with a scanned data value below the dust detection threshold as abnormal pixels. The dust detection threshold for determining abnormal pixels is set based on the average luminance value (average value of scanned data) of each pixel in one line in the main scanning direction. Note that, in order to perform multiple scans, the average luminance value for each line may be used as the dust detection threshold. The CPU 301 stores the positions of the detected abnormal pixels in a memory such as the RAM 303 (S118). This allows only pixels containing dust in the area from position P2 to position P3 to be detected. The CPU 301 reverses the rotation of the optical system motor 225, moving the front surface scanning unit 104 from position P3 to the HP position (P1) as shown in FIG. 5(c), thereby completing abnormal pixel detection (S119).

[0063] (Abnormal pixel correction) 10 is a flowchart showing the correction process for the detected abnormal pixel. After detecting the abnormal pixel by the process of FIG. 8, the front surface reading unit 104 waits at the HP position (P1) with the LED 105 turned on.

[0064] 5(d), the CPU 301 drives the optical system motor 225 to start moving the front surface reading unit 104 from the HP position to position P3 (S120). The CPU 301 reads the front surface white reference member 103 multiple times between positions P2 and P3 while moving the front surface reading unit 104 with the settings for normal image reading (S121).

[0065] The CPU 301 waits until the front surface reading unit 104 moves to position P3 and finishes reading the front surface white reference member 103 (S122: N). When reading is finished (S122: Y), the CPU 301 performs abnormal pixel correction on the reading result (read data) of the front surface white reference member 103 (S123).

[0066] FIG. 11 is an explanatory diagram of the results of abnormal pixel correction. The shading correction data obtained from the read data includes an abnormal value due to a foreign object at pixel B. When correcting the abnormal value of an abnormal pixel (pixel B), linear interpolation is performed using the shading correction data of normal-value pixels (reference pixels) adjacent to the abnormal pixel. In FIG. 11, the abnormal pixel B is interpolated using an interpolation pixel included in the reference pixels. This generates shading correction data in which the influence of the abnormal pixel is suppressed.

[0067] (Reading the manuscript) 12 is a flowchart showing the process of reading an original by the automatic document reader 10 configured as described above. The process of reading one side (front side) of an original in the flow reading mode using the ADF 20 is shown in FIG.

[0068] The CPU 301 of the reader 40 waits until it receives a reading start instruction from the CPU 311 of the controller 310 (S101: N). As described above, the CPU 311 of the controller 310 receives an instruction to start an image reading job from the operation unit 90 or an external device such as a personal computer, and transmits the reading start instruction to the CPU 301 of the reader 40. Upon receiving the reading start instruction (S101: Y), the CPU 311 transmits the reading start instruction to the CPU 301 of the reader 40. Upon receiving the reading start instruction from the CPU 311, the CPU 301 performs an abnormal pixel detection process for the front white reference member 103 shown in FIG. 8 (S102).

[0069] After executing the abnormal pixel detection process, the CPU 301 performs an abnormal pixel correction process for the front white reference member 103 shown in FIG. 10 (S103). When the abnormal pixel correction process is completed, the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the reading start position Ps shown in FIG. 5(e) and starts reading the original (S104). When the front surface reading unit 104 has completely moved to the reading start position Ps, the CPU 301 starts transporting the original by the ADF 20 to the reading position of the front surface reading unit 104 and reads the original. The front surface reading unit 104 repeatedly reads the transported original line by line.

[0070] The CPU 301 waits until reading of all the documents is completed (S105: N). The CPU 301 determines that reading of all the documents is completed when, for example, it is detected that there are no documents left on the document tray 121 based on the detection results of the first document presence detection sensor 204 and the second document presence detection sensor 205. When reading of all the documents is completed (S105: Y), the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (P1) and ends the process (S106).

[0071] In the above example, the case of skimming reading has been described, but in the case of fixed reading, the document is placed on the document glass 101. When the processes of S101 to S103 are completed, the CPU 301 moves the front surface reading unit 104 to the reading start position Ps. Thereafter, the CPU 301 moves the front surface reading unit 104 in the sub-scanning direction, repeatedly reading the document placed on the document glass 101 line by line.

[0072] As described above, the automatic document reading device 10 (reader 40) of this embodiment reads the front white reference member 103 while moving the front reading unit 104 when detecting and correcting abnormal pixels on the front white reference member 103. This allows the automatic document reading device 10 (reader 40) to detect abnormal pixels on the white reference member without being affected by unevenness on the surface of the white reference member, even when an inexpensive white reference member is used. This enables accurate shading correction.

[0073] (Second embodiment) The configuration of the automatic document reading device 10 and the configuration of the control system of the second embodiment are the same as those of the first embodiment, so a description of the configuration of the automatic document reading device 10 and the configuration of the control system will be omitted. In the second embodiment, the processing other than the detection of abnormal pixels of the front white reference member 103 is the same as that of the first embodiment, so a description of the similar processing will be omitted.

[0074] In the second embodiment, abnormal pixel detection for the front white reference member 103 is performed based on the reading results (read data) obtained by the front reading unit 104 of the front white reference member 103. A case where foreign matter (dust) adheres to the positions (pixel A, pixel B) illustrated in FIG. 9(a) will be described. FIG. 13 is a flowchart showing the abnormal pixel detection process. FIG. 14 is an explanatory diagram of abnormal pixel detection.

[0075] 8, the CPU 301 moves the front surface reading unit 104 to the HP position and performs black level adjustment (S610, S611). The CPU 301 turns on the LED 105 (S612), drives the optical system motor 225, and starts moving the front surface reading unit 104 from the HP position to position P3 (S613), as shown in FIG.

[0076] The CPU 301 moves the front surface reading unit 104 and continuously reads the front surface white reference member 103 from position P2 to position P3 (S614). The CPU 301 waits until reading from position P2 to position P3 is complete (S615: N). When reading is complete (S615: Y), the CPU 301 performs abnormal pixel detection on the front surface white reference member 103 (S616).

[0077] The brightness values ​​of the read results (read data) between positions P2 and P3 of the front white reference member 103 are uneven overall due to the unevenness of the surface, as shown in the example in FIG. 14. The brightness value of pixel B is extremely lower than that of the other pixels. The dust detection threshold for determining abnormal pixels is set based on the average brightness value (average value of read data) for each predetermined width in the main scanning direction. In FIG. 14, one line in the main scanning direction is divided into multiple sections, first to fifth dust detection sections, and a dust detection threshold is set for each dust detection section.

[0078] The CPU 301 detects the position of a pixel (here, pixel B) whose brightness value is equal to or less than the dust detection threshold as an abnormal pixel, and stores the position of the detected abnormal pixel in a memory such as the RAM 303 (S617). This allows the position of the abnormal pixel to be accurately detected even if the reading result (read data) is uneven. The CPU 301 reverses the rotation of the optical system motor 225, and moves the front surface reading unit 104 from position P3 to the HP position (P1) as shown in FIG. 5(c), thereby completing the abnormal pixel detection (S618).

[0079] In the second embodiment, as in the first embodiment, even when an inexpensive white reference member is used, it is possible to detect abnormal pixels on the white reference member without being affected by the unevenness of the surface of the white reference member. This enables accurate shading correction. Furthermore, even if the read data is uneven across the entire main scanning direction, accurate detection of abnormal pixels is possible by dividing the main scanning direction into multiple sections and setting a threshold value for each section.

[0080] (Third embodiment) The configuration of the automatic document reader 10 and the configuration of the control system of the third embodiment are the same as those of the first embodiment, so a description of the configuration of the automatic document reader 10 and the configuration of the control system will be omitted. The abnormal pixel detection process of the third embodiment is the same as that of the first embodiment, so a description thereof will be omitted. Note that the abnormal pixel detection process of the second embodiment is also effective in the third embodiment. The abnormal pixel correction process and document reading process of the third embodiment differ from those of the first and second embodiments.

[0081] FIG. 15 is a flowchart showing the abnormal pixel correction process of the third embodiment. The CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (S250). Note that if the front surface reading unit 104 is already at the HP position, the process of S250 is omitted. The CPU 301 performs black level adjustment by having the front surface reading unit 104 read the front surface white reference member 103 at the HP position with the LED 105 turned off (S251). This is the same process as the process of S111 in FIG. 8. Thereafter, the CPU 301 turns on the LED 105 (S252). The CPU 301 performs correction of abnormal pixels by processes similar to the processes of S120 to S123 in FIG. 10 of the first embodiment (S253 to S256).

[0082] The shading correction data generated based on the reading results (read data) of the front white reference member 103 obtained in the process of S254 is similar to the shading correction data obtained in the process of S121 in Fig. 10 of the first embodiment. In this case, it is as shown in Fig. 11. As in the first embodiment, abnormal pixel correction is performed by linearly interpolating the shading correction data of the abnormal pixel with the shading correction data of the normal pixel adjacent to the abnormal pixel, as shown in Fig. 11. This makes it possible to obtain shading correction data in which the influence of the abnormal pixel is suppressed.

[0083] 16 is a flowchart showing the process of reading an original document in the third embodiment, which is a process of reading one side (front side) of an original document in the flow reading mode using the ADF 20.

[0084] The CPU 301 waits until the automatic document reading device 10 is powered on (S201: N). When the power is turned on (S201: Y), the CPU 301 performs the above-described abnormal pixel detection process for the front white reference member 103 and stores the abnormal pixel positions (S202). After the abnormal pixel detection process, the CPU 301 turns off the LED 105 (S203) and waits until the above-described reading start instruction is obtained (S204: N).

[0085] When the CPU 301 receives a reading start instruction from the CPU 311 (S204: Y), it performs the abnormal pixel correction process shown in Fig. 15 (S205). After the abnormal pixel correction process is completed, the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the reading start position Ps in Fig. 5(e) and reads the document (S206). This process is the same as S104 in Fig. 12.

[0086] 12, the CPU 301 waits until reading of all documents is completed (S207: N). When reading of all documents is completed (S207: Y), the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (P1) (S208). After moving the front surface reading unit 104 to the HP position (P1), the CPU 301 repeats the processes of S204 to S208 until the power is turned off (S209: N). When the power is turned off (S209: Y), the CPU 301 ends the document reading process.

[0087] In the above example, the case of skimming reading has been described, but in the case of fixed reading, the document is placed on the document glass 101. When the processes of S201 to S205 are completed, the CPU 301 moves the front surface reading unit 104 to the reading start position Ps. Thereafter, the CPU 301 moves the front surface reading unit 104 in the sub-scanning direction, repeatedly reading the document placed on the document glass 101 line by line.

[0088] 16, in the processes of S201 and S209, it is determined whether the power of the automatic document reader 10 has been operated, but this determination may be a determination of the power saving state (sleep state). That is, the CPU 301 waits for recovery from the power saving state in the process of S201, and determines whether to transition to the power saving state in the process of S209.

[0089] In the third embodiment described above, when detecting and correcting abnormal pixels on the white reference member, the front white reference member 103 is read while the front reading unit 104 is moving. Therefore, even when an inexpensive white reference member is used, it is possible to detect abnormal pixels on the white reference member without being affected by the unevenness of the surface of the white reference member. This enables accurate shading correction. Furthermore, by detecting abnormal pixels on the white reference member in advance when the automatic document reading device 10 is started (when the power is turned on or when returning from a power-saving state), the time from the start to the end of reading can be shortened.

[0090] (Fourth embodiment) The configuration of the automatic document reading device 10 and the configuration of the control system of the fourth embodiment are the same as those of the first embodiment, so descriptions of the configuration of the automatic document reading device 10 and the configuration of the control system will be omitted. In the fourth embodiment, the abnormal pixel detection process is the same as that of the first or second embodiment, so descriptions will be omitted. In the fourth embodiment, the abnormal pixel correction process is the same as that of the third embodiment, so descriptions will be omitted.

[0091] In the fourth embodiment, it is detected that a document has been placed on the document tray 121 of the ADF 20 or on the document platen glass 101. When the first document presence detection sensor 204 detects a document, it can be determined that a document has been placed on the document tray 121 of the ADF 20. When the first document presence detection sensor 204 does not detect a document, it can be determined that the document has been removed from the document tray 121.

[0092] The placement of a document on the platen glass 101 can be detected by providing a sensor below the platen glass 101. FIG. 17 is an explanatory diagram of a sensor provided below the platen glass 101. In FIG. 17, a plurality of document detection sensors 180, 181, 182, and 183 are provided below the platen glass 101 to detect the presence or absence of a document on the platen glass 101. If at least one of the document detection sensors 180, 181, 182, and 183 detects a document, it can be determined that a document is placed on the platen glass 101. If none of the document detection sensors 180, 181, 182, and 183 detects a document, it can be determined that the document has been removed from the platen glass 101. The document detection sensors 180, 181, 182, and 183 are, for example, optical sensors, and can detect the presence or absence of a document based on whether light irradiated toward the platen glass 101 is reflected.

[0093] When a document is detected both on document tray 121 of ADF 20 and on document glass 101, it is determined that a document is placed on document tray 121. When a document is not detected on either, it is determined that a document is placed on document glass 101.

[0094] Fig. 18 is a flowchart showing the process of reading an original document according to the fourth embodiment. Fig. 18 shows the process of reading one side (front side) of an original document.

[0095] As in S101 of FIG. 12, the CPU 301 determines whether a read start instruction has been received (S301). If a read start instruction has not been received (S301: N), the CPU 301 determines whether a document has been placed on the document tray 121 of the ADF 20 or on the document glass 101 (S302). If a document has not been placed on either tray (S302: N), the CPU 301 returns to the process of S301 and determines whether a read start instruction has been received. If it determines that a document has been placed (S302: Y), the CPU 301 determines whether a predetermined time has elapsed since the previous abnormal pixel detection process (S303). To this end, the CPU 301 incorporates a timer that measures the elapsed time since the previous abnormal pixel detection process. If the predetermined time has elapsed (S303: Y), the CPU 301 performs the above-described abnormal pixel detection process (S304). The predetermined time in S303 is, for example, 6 hours, but may also be 0. When the predetermined time is 0 hours, the abnormal pixel detection process is performed every time a document is placed.

[0096] If the predetermined time has not elapsed (S303: N), or after the abnormal pixel detection process has been performed, the CPU 301 turns off the LED 105 of the front surface reading unit 104 (S305). The CPU 301 turns on a flag (abnormal pixel detection execution flag) indicating that abnormal pixel detection has been performed (S306). The abnormal pixel detection execution flag is held in the RAM 303.

[0097] Thereafter, CPU 301 determines whether or not a read start instruction has been acquired (S307), similar to the processing of S301. If a read start instruction has not been acquired (S307: N), CPU 301 determines whether or not the document has been removed (S308). If the document has been removed (S308: Y), CPU 301 returns to the processing of S301 and determines whether or not a read start instruction has been acquired. If the document has not been removed (S308: N), CPU 301 returns to the processing of S307 and determines whether or not a read start instruction has been acquired.

[0098] When a reading start instruction is received from the CPU 311 in the process of S301 or S307 (S301: Y or S307: Y), the CPU 301 determines whether the abnormal pixel detection execution flag stored in the RAM 303 is on (S309). If the abnormal pixel detection execution flag is not on (S309: N), the CPU 301 performs the abnormal pixel detection process (S310) because the abnormal pixel detection process for the front white reference member 103 has not been performed. If the abnormal pixel detection execution flag is on (S309: Y), or after the abnormal pixel detection process has been performed, the CPU 301 performs the above-described abnormal pixel correction process (S311).

[0099] This completes the abnormal pixel detection process and the abnormal pixel correction process for the front white reference member 103. After that, the CPU 301 drives the optical system motor 225 to move the front reading unit 104 to the reading start position Ps in FIG. 5(e) and reads the original (S312). If an original is placed on the ADF original tray 121, the original is read in the flow reading mode. If an original is placed on the platen glass 101, the original is read in the fixed reading mode.

[0100] As in the process of S105, the CPU 301 waits until reading of all documents is completed (S313: N). When reading of all documents is completed (S313: Y), the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (P1) (S314). This completes the document reading process.

[0101] In the fourth embodiment described above, when detecting and correcting abnormal pixels on the white reference member, the front white reference member 103 is read while the front reading unit 104 is moving. Therefore, even when an inexpensive white reference member is used, it is possible to detect abnormal pixels on the white reference member without being affected by the unevenness of the surface of the white reference member. This enables accurate shading correction. Furthermore, because the detection of abnormal pixels on the white reference member is performed in advance when a document is placed on the document tray 121 or the document platen glass 101, the time from the start to the end of document reading can be shortened.

[0102] (Fifth embodiment) The configuration of the automatic document reading device 10 and the configuration of the control system in the fifth embodiment are the same as those in the first embodiment, so a description of the configuration of the automatic document reading device 10 and the configuration of the control system will be omitted. In the fifth embodiment, the abnormal pixel detection process is the same as that in the first or second embodiment, so a description thereof will be omitted. In the fifth embodiment, the abnormal pixel correction process is the same as that in the first or third embodiment, so a description thereof will be omitted. In the fifth embodiment, like the fourth embodiment, the placement of an original on the document tray 121 or the document glass 101 is detected.

[0103] Fig. 19 is a flowchart showing the process of reading a document in the fifth embodiment. Fig. 19 shows the process of reading one side (front side) of a document.

[0104] Similar to the processes of S301 and S302 of FIG. 18 in the fourth embodiment, the CPU 301 waits for a read start instruction and determines whether a document has been placed (S401, S402). If a read start instruction is not received and a document has been placed (S401: N, S402: Y), the CPU 301 performs the above-described abnormal pixel detection process (S403). When the abnormal pixel detection process is completed, the CPU 301 performs the above-described abnormal pixel correction process (S404). The CPU 301 turns on a flag indicating that abnormal pixel detection has been performed (abnormal pixel detection execution flag) (S405). The abnormal pixel detection execution flag is held in the RAM 303.

[0105] Thereafter, similarly to the processing of S401, CPU 301 determines whether or not a reading start instruction has been acquired (S406). If a reading start instruction has not been acquired (S406: N), CPU 301 determines whether or not the document has been removed (S407). If the document has not been removed (S407: N), CPU 301 determines whether or not a predetermined time has elapsed since the abnormal pixel detection execution flag was set to ON (S408). The predetermined time is, for example, 15 seconds. If the predetermined time has not elapsed (S408: N), CPU 301 returns to the processing of S406 and determines whether or not a reading start instruction has been acquired.

[0106] If the predetermined time has elapsed (S408: Y) or the document has been removed (S407: Y), the CPU 301 turns off the abnormal pixel detection execution flag (S409). That is, the CPU 301 turns off the abnormal pixel detection execution flag if a reading start instruction is not received even though a predetermined time has elapsed since the abnormal pixel detection execution flag was set on by the processes of S406 to S408. Furthermore, the CPU 301 turns off the abnormal pixel detection execution flag if the document is removed even before the predetermined time has elapsed since the abnormal pixel detection execution flag was set on.

[0107] After setting the abnormal pixel detection execution flag to OFF, the CPU 301 turns off the LED 105 (S410) and moves the front surface reading unit 104 to the HP position (P1) (S411). After that, the CPU 301 returns to the process of S401 and waits for an instruction to start reading.

[0108] When a reading start instruction is received from the CPU 311 in the process of S401 or S406 (S401: Y or S407: Y), the CPU 301 determines whether the abnormal pixel detection execution flag stored in the RAM 303 is on (S420). If the abnormal pixel detection execution flag is not on (S420: N), the CPU 301 determines that the abnormal pixel detection process and the abnormal pixel correction process for the front white reference member 103 have not been performed, and performs the abnormal pixel detection process and the abnormal pixel correction process again (S421, S422).

[0109] If the abnormal pixel detection execution flag is on (S420: Y), or after the abnormal pixel detection process and the abnormal pixel correction process have been executed, the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the reading start position Ps and reads the document (S423). If a document is placed on the document tray 121 of the ADF, the document is read in the flow reading mode. If a document is placed on the document platen glass 101, the document is read in the fixed reading mode.

[0110] As in the process of S105, the CPU 301 waits until reading of all documents is completed (S424: N). When reading of all documents is completed (S424: Y), the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (P1) (S425). This completes the document reading process.

[0111] In the fifth embodiment described above, when detecting and correcting abnormal pixels on the white reference member, the front white reference member 103 is read while the front reading unit 104 is moving. Therefore, even when an inexpensive white reference member is used, it is possible to detect abnormal pixels on the white reference member without being affected by the unevenness of the surface of the white reference member. This enables accurate shading correction. Furthermore, by detecting and correcting abnormal pixels on the white reference member in advance when a document is placed on the document tray 121 or the document glass 101, the time from the start to the end of document reading can be shortened.

[0112] (Sixth embodiment) The configuration of the automatic document reading device 10 and the configuration of the control system in the sixth embodiment are the same as those in the first embodiment, so a description of the configuration of the automatic document reading device 10 and the configuration of the control system will be omitted. In the sixth embodiment, the abnormal pixel detection process is the same as that in the first or second embodiment, so a description thereof will be omitted. In the sixth embodiment, like the fourth embodiment, the placement of an original on the document tray 121 or the document glass 101 is detected.

[0113] The abnormal pixel correction process of the sixth embodiment will be described. The abnormal pixel correction process of the sixth embodiment is executed by one of two processes depending on the execution status of the abnormal pixel detection process. When the abnormal pixel correction process is executed following the abnormal pixel detection process, the CPU 301 executes the process of the flowchart shown in FIG. 10 of the first embodiment. When the abnormal pixel correction process is executed independently, the CPU 301 executes the process of the flowchart shown in FIG. 15 of the third embodiment.

[0114] Fig. 20 is a flowchart showing the process of reading an original document in the sixth embodiment, which is a process of reading one side (front side) of an original document.

[0115] Similar to the processes of S301 and S302 of FIG. 18 in the fourth embodiment, the CPU 301 waits for a read start instruction and determines whether a document has been placed (S501, S502). If a read start instruction is not received and a document has been placed (S501: N, S502: Y), the CPU 301 performs the above-described abnormal pixel detection process (S503). Upon completion of the abnormal pixel detection process, the CPU 301 performs the abnormal pixel correction process shown in FIG. 10 (S504). The CPU 301 turns on a flag indicating that abnormal pixel detection has been performed (abnormal pixel detection execution flag) and a flag indicating that abnormal pixel correction has been performed (abnormal pixel correction execution flag) (S505). The abnormal pixel detection execution flag and the abnormal pixel correction execution flag are held in the RAM 303.

[0116] Thereafter, the CPU 301 determines whether or not a read start instruction has been acquired, similar to the processing of S501 (S506). If a read start instruction has not been acquired (S506: N), the CPU 301 determines whether or not the document has been removed (S507). If the document has not been removed (S507: N), the CPU 301 determines whether or not a predetermined time has elapsed since the abnormal pixel detection execution flag and the abnormal pixel correction execution flag were set to ON (S508). The predetermined time is, for example, 15 seconds. If the predetermined time has not elapsed (S508: N), the CPU 301 returns to the processing of S506 and determines whether or not a read start instruction has been acquired.

[0117] If the predetermined time has elapsed (S508: Y) or the document has been removed (S507: Y), the CPU 301 turns off the abnormal pixel correction execution flag (S509). That is, the CPU 301 turns off the abnormal pixel correction execution flag if a reading start instruction is not received even though a predetermined time has elapsed since the abnormal pixel correction execution flag was set on by the processes of S506 to S508. Furthermore, the CPU 301 turns off the abnormal pixel correction execution flag if the document is removed even before the predetermined time has elapsed since the abnormal pixel correction execution flag was set on.

[0118] After setting the error pixel correction execution flag to OFF, the CPU 301 turns off the LED 105 (S510) and moves the front surface reading unit 104 to the HP position (P1) (S511). After that, the CPU 301 returns to the process of S501 and waits for an instruction to start reading.

[0119] When a reading start instruction is received from the CPU 311 in the process of S501 or S506 (S501: Y or S506: Y), the CPU 301 determines whether the abnormal pixel detection execution flag stored in the RAM 303 is on (S520). If the abnormal pixel detection execution flag is not on (S520: N), the CPU 301 determines that the abnormal pixel detection process and the abnormal pixel correction process for the front white reference member 103 have not been performed, and performs the abnormal pixel detection process and the abnormal pixel correction process again (S521, S522). In this case, the abnormal pixel detection process and the abnormal pixel correction process are performed consecutively, so the CPU 301 performs the abnormal pixel correction process shown in FIG. 10.

[0120] If the abnormal pixel detection execution flag is on (S520: Y), the CPU 301 determines whether the abnormal pixel correction execution flag saved in the RAM 303 is on (S523). If the abnormal pixel correction execution flag is not on (S523: N), the CPU 301 determines that the abnormal pixel correction process has not been performed on the front white reference member 103, and performs the abnormal pixel correction process again (S524). In this case, the abnormal pixel correction process is performed independently, so the CPU 301 performs the abnormal pixel correction process shown in FIG. 15.

[0121] If the abnormal pixel correction execution flag is on (S523: Y), the abnormal pixel detection process and the abnormal pixel correction process are completed after the abnormal pixel correction process of S522 or the abnormal pixel correction process of S524. In this case, the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the reading start position Ps and reads the document (S525). If a document is placed on the document tray 121 of the ADF, the document is read in the flow reading mode. If a document is placed on the document platen glass 101, the document is read in the fixed reading mode.

[0122] As in the process of S105, the CPU 301 waits until reading of all documents is completed (S526: N). When reading of all documents is completed (S526: Y), the CPU 301 drives the optical system motor 225 to move the front surface reading unit 104 to the HP position (P1) (S527). This completes the document reading process.

[0123] In the sixth embodiment described above, when detecting and correcting abnormal pixels on the white reference member, the front white reference member 103 is read while the front reading unit 104 is moving. Therefore, even when an inexpensive white reference member is used, it is possible to detect abnormal pixels on the white reference member without being affected by the unevenness of the surface of the white reference member. This enables accurate shading correction. Furthermore, by detecting and correcting abnormal pixels on the white reference member in advance when a document is placed on the document tray 121 or the document glass 101, the time from the start to the end of reading can be shortened.

[0124] In the first to sixth embodiments, the CPU 301 performs shading correction on the read data obtained by reading the document based on the shading correction data using the image processing unit 306. This makes it possible to perform shading correction with high accuracy even when foreign matter is attached to the front white reference member 103, thereby enabling high-precision reading of the document.

[0125] (Image forming system) 21 is a configuration diagram of an image forming system including the automatic document reading device 10 described in the first to sixth embodiments, an image forming device, and an operation unit 90. In this image forming system 1, a reader 40 is provided on the image forming device 50, and an ADF 20 is provided on the reader 40. The operation unit 90 is provided in front of the automatic document reading device 10 and the image forming device 50. Such an image forming system 1 realizes a highly functional image forming device such as a copier, a multifunction machine, or an MFP.

[0126] When copying an original, the image data generated by the reader 40 reading the original is sent to the image forming device 50. This image data undergoes shading correction using shading correction data. The image forming device 50 forms an image on paper based on the image data obtained from the reader 40. The image forming device 50 forms the image on paper using a method commonly used for image formation, such as an electrophotographic method or an inkjet method. Since the time from the start to the end of reading by the reader 40 is shortened, the first copy output time is shortened.

[0127] The image forming apparatus 50 may be connected to an external device via a predetermined network. In this case, the image forming apparatus 50 may transmit image data obtained from the reader 40 to the external device.

Claims

1. A reference member; a reading means for reading the document or the reference member; a moving means for moving the reading means in a document transport direction to a first region for reading the document and a second region for reading the reference member; a control means for performing shading correction; the control means moves the reading means in the transport direction from outside the second area to inside the second area, and performs a first reading operation to read the reference member in the second area; after performing the first reading operation, moves the reading means again from outside the second area to inside the second area, and performs a second reading operation to read the reference member in the second area; and performs the shading correction using the first reading result read in the first reading operation and the second reading result read in the second reading operation. Image reading device.

2. The control means detecting an abnormal pixel where the first reading result is an abnormal value based on the first reading result obtained by causing the reading means to read different positions within the second area of ​​the reference member a plurality of times by the first reading operation and a predetermined threshold value; correcting the abnormal pixels based on the second reading results obtained by causing the reading means to read different positions within the second area of ​​the reference member a plurality of times in the second reading operation, and generating shading correction data; a reading unit for reading the document and a shading correction data for correcting the shading of the document; 2. The image reading device according to claim 1.

3. The control means detects the abnormal pixel based on second data obtained by shading correcting the first reading result obtained by making the reading means read different positions of the second area of ​​the reference member a plurality of times, using first data obtained from the reading result obtained by making the reading means read a first position outside the second area of ​​the reference member.

3. The image reading device according to claim 2.

4. the control means causes the reading means to read the second area of ​​the reference member a plurality of times, and sets an average value of the read results of each pixel of the read results obtained as the threshold value, and detects the abnormal pixel by comparing the second data with the threshold value.

4. The image reading device according to claim 3.

5. the control means divides one line of the read result obtained by causing the reading means to read the second area of ​​the reference member a plurality of times into a plurality of sections, and sets an average value of the read result of the pixels in each section as the threshold value for each section.

5. The image reading device according to claim 4.

6. the control means generates the shading correction data by correcting the abnormal pixel based on the second reading result of a pixel adjacent to the abnormal pixel in a line direction.

3. The image reading device according to claim 2.

7. The control unit detects the abnormal pixel by receiving an instruction to start reading the document, and corrects the abnormal pixel after detecting the abnormal pixel.

3. The image reading device according to claim 2.

8. the control means detects the abnormal pixel before receiving an instruction to start reading the document, and corrects the abnormal pixel after receiving the instruction to start reading the document.

3. The image reading device according to claim 2.

9. The control means detects the abnormal pixel when the image reading device is started up.

9. The image reading device according to claim 8.

10. a placement means on which the document is placed; and a document detection means for detecting the document placed on the placement means, The control means detects the abnormal pixel when the document detection means detects the document.

9. The image reading device according to claim 8.

11. the placement unit is a tray provided in a transport unit that transports the document to a reading position of the reading unit, The document detection means detects the document placed on the tray.

11. The image reading device according to claim 10.

12. the placing means is a document table glass, The document detection means detects a document placed on the document table glass.

11. The image reading device according to claim 10.

13. The method further includes a timer for measuring the time elapsed since the previous detection of the abnormal pixel, The control means detects the abnormal pixel when a predetermined time has elapsed since the document detection means detected the document and the previous detection of the abnormal pixel.

11. The image reading device according to claim 10.

14. the control means detects the abnormal pixel before receiving an instruction to start reading the document, and corrects the abnormal pixel before receiving the instruction to start reading the document.

3. The image reading device according to claim 2.

15. a placement means on which the document is placed; and a document detection means for detecting the document placed on the placement means, The control means detects the abnormal pixels when the document detection means detects the document, and corrects the abnormal pixels after detecting the abnormal pixels.

15. The image reading device according to claim 14.

16. The method further includes a timer for measuring the time elapsed since the previous detection of the abnormal pixel, the control means detects the abnormal pixel again when a predetermined time has elapsed since the previous detection of the abnormal pixel and an instruction to start reading the document has been received; The control unit corrects the abnormal pixel again when a predetermined time has elapsed since the previous detection of the abnormal pixel and an instruction to start reading a document has been obtained.

16. The image reading device according to claim 15.

17. The method further includes a timer for measuring the time elapsed since the previous detection of the abnormal pixel, The control unit corrects the abnormal pixels again when a predetermined time has elapsed since the previous correction of the abnormal pixels and an instruction to start reading a document has been obtained.

16. The image reading device according to claim 15.

18. The image reading device according to claim 1; and an image forming device that forms an image on a sheet based on image data generated by the image reading device through shading correction of the reading result of the document. Imaging system.

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